Electro-static switching apparatus



June 16, 1959 R. M. WALKER ELECTRO-STATIC SWITCHING APPARATUS 2Sheets-Sheet 1 Filed Oct. 21, 1955 N 7. Z Z ch TH w a A L 0 MM 1 w R T ax T L N A w 2; P M 0 am 5 INVENTOR. faster M. ham 5e United StatesPatent ELECTRO-STATIC SWITCHIN G APPARATUS Robert M. Walker, Closter,N.J., assignor to International Business Machines Corporation, acorporation of New York Application October 21, 1955, Serial No. 541,922

1 Claim. (Cl. 250-27) The present invention pertains to improvements inelectro-static switching apparatus.

An object of the invention is to provide an improved electro-statictable look-up system for generating generalized switching functions inlarge numbers of variables.

A further object of the invention is to provide electrostatic functionswitching means adapted to give improved distinction between read-outsignals derived from electron bombardments directed by dilfering inputcombinations.

A further object is to provide apparatus of the above nature for use indevices employed in automation control systems and the like, and whereinthe output signals representative of two differing input combinationsmay be of maximum amplitude but of opposite polarity.

A further object is to provide apparatus of the above type adapted toestablish simultaneous individual amplifications of signals derived frompreviously selected and unselected target areas of a cathode ray tube,while differentially combining the two amplified pulses to produce asingle output pulse of distinctive character.

Another object is to provide apparatus of the above nature in which theoutput signals may be picked up from two separate but inter-relatedsystems of backing electrodes disposed on the outer face of the cathoderay tube, performing the above noted advantageous functions without thenecessity for complicated structures within the tube.

A further object is to provide apparatus of the above nature which isreadily adaptable to various special functional processes.

Other objects and advantages of the invention will become evident duringthe course of the following description in connection with theaccompanying drawings, in which:

Figure 1 is a diagrammatic longitudinal view of a cathode ray tubesuitable for use in the invention;

Figure 2 is a block diagram illustrating a preferred arrangement of maincomponents of the system;

Figure 3 illustrates the outputs from a typical row of the pick-upelectrodes shown in Fig. 2;

Figure 4 is a circuit diagram of a typical arrangement of the primarysignal and dilferential amplifiers;

Figure 5 illustrates a pluggable form of the pick-up electrodeconnections by which various optional arrangements may readily be set upfor different functional requirements, and

Figure 6 shows one form of alternative electrode arrangement as providedby the apparatus illustrated in Figure 5.

Referring to Figure l, the numeral 10 generally designates a typicalcathode ray tube comprising an envelope 11 coated on its interiorlateral portion with a conducting material 12, and having the glass endscreen portion 13 1nteriorly coated with a suitable phosphor 14. Thetube 19 and 20, and horizontal deflector plates 21 and 22.

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An array of small conducting electrodes 23, '24, 25, 26, 27, 28, 29, 30,etc. is attached to the outer surface of the endscreen portion 13. Insimplest form as illustrated in Figures 1 and 2, these electrodes aredivided into two electrically separated groups (a) and (b), theelectrodes of group (a) being connected to a common output conductor31a, while those of group (b) are similarly connected to a conductor3211. By reference to Figure 2 it will be seen that the typical array ofsixty-four individual electrodes is arranged in rectangular form withthe electrodes of the two groups interspersed in an arbitrary mannerdetermined by the requirements of a particular combinational problem tobe resolved. Thus in the fifth horizontal row, electrodes 23, 25, 26, 27and 29 are connected to output conductor 31a, while the electrodes 24,28 and 30 are all connected to conductor 32b, various other respectiveconnective combinations being provided throughout the remainder of thearray. It will be understood, however, that the device is not limited tothe exact number or combinational arrangement shown for illustration,since as hereinafter set forth, the pick-up array is adapted to manyother arrangements set up for dealing with different types of problems.

The conductor 31a comprises the input connection to a primary amplifier33, while conductor 32b similarly leads '1 to a second primary amplifier34. The amplifiers 33 and 34 are preferably of similar or identicalconstruction as shown in Figure 4. Referring to the latter figure, itwill be noted that the illustrated amplifier 33 is a three stage typeemploying pentodes 35, 36 and 37, the control grid 38 of the first tube35 being connected. to the conductor 3111 via a condenser 39, while inthe second primary amplifier 34 the control grid 40 of the first tube 41re ceives its signal from the pick-up conductor 32b via a condenser 42.

The outputs 43 and 44 of the amplifiers 33 and 34 jointly feed adifferential amplifier 45, also shown in illustrative detail in Figure4. This amplifier employs a double triode 46 having its left andright-hand grids 47 and 48 connected to conductors 43 and 44respectively. The two tube circuits are in parallel, separated on the B+side by a resistor 49 as shown. A common output 50 is taken via acondenser 51 from the left-hand side of the dual network. Theillustrated components of the system are so proportioned that the singleamplified signal at the output conductor 50 is representative of thedifference potential between the two simultaneous inputs and is positiveor negative in sign dependent on which of the two grid potentials ispreponderant. Thus if the lefthand grid 47 is driven a certain amountpositive while the right remains at or is driven to a lower potential,the output is positive, while if the right grid 48 is driven positivewhile the left is at lower potential the output is negative, the outputamplitude in each case being a function of the net input difference. Foractuation and control of the CRT 10, the system is provided with a pulsegenerator and control network 69, selector switches 61, and deflectionamplifier 62. These units are shown in block diagram, Figure 1, as theinternal structures and operation of suitable devices of this nature arewell known in the electronic art and hence do not call for detaildescription herein.

A typical operation of the switching system is as follows, it beingborne in mind that the pick-up electrode array has been arranged inaccordance with a specific problem:

The particular test values of the variables of the problem are appliedin terms of deflecting voltages to the tube 10 and the beam is turned onfor a short period such as 10 microseconds, the combination ofdeflecting voltage determining a particular spot of the inner targetsurface I4 upon which the beam impinges, i.e., an X, Y position behindone of the external pick-up electrodes. In preferred practice the beamis moved laterally across the selected target area during the above timeperiod, this movement being designed to erase the charge at the initialposition of contact to ensure that a pulse will again be obtained if thesame target is again selected Within a short time.

When the beam is thus applied to the selected target spot, the result isa positive pulse at the output of the primary amplifier to which theselected pick-up electrode is connected. At the same time, due toproximity effects, lesser signals are picked up by neighboring,unselected electrodes and transmitted to their respective primaryamplifiers or amplifier. In the case of unselected electrodes of thesame (a) or (b) group as the selected. spot, the effect obviously is toincrease the signal to the latters primary amplifier, while the otherprimary amplifier receives any signal effects from electrodes of theother group and. produces its own corresponding output. However, thesignal from the selected target is always preponderant (a typical ratiobeing about four to one), so that the final output from the differentialamplifier in each case is a sharp and distinctive pulse, positive if thecombination of controlling variable values fulfills a yes condition ofthe problem and negative if the control combination selects a no.

To illustrate, referring to Figures 2 and 3, if control combinations areapplied which direct the electron beam to target areas behind thedesignated electrodes, electrodes 23, 25, 26, 27 and 29 will report yesby sharp positive output pulses as illustrated in Fig. 3, whileelectrodes 24, 28 and 30 will report no by similarly sharp anddistinctive negative pulses. The assignment of positive sign to yes andnegative to no is purely arbitrary, since obviously the reverseassignment may be made if called for by the nature of the process towhich the system is applied. In either case, however, it will be seenthat the differential combination provides sharp and completelyunmistakable distinction between yes and no signals by difference inpolarity rather than simply by difference in magnitude. The advantagesin point of precision, reliability and adaptability will be evident. Afurther advantage is the tendency to balance out unwanted generaleffects such as electron cloud pulses.

For convenience in explanation, the apparatus has been depicted with atypical array of 64 pick-up electrodes. It will be understood, however,that the target array may be made to include larger numbers ofelectrodes limited only by the available operative area of the tube. Forinstance, using a single five-inch cathode ray tube and typicalelectrodes of .145 inch diameter spaced on .2 inch centers, 256electrodes may be accommodated, capable of producing any switchingfunction up to 8 variables. As generalized switching functions of morethan four variables are usually complicated and expensive to produce bydiode and vacuum tube circuits, it will be evident that the presentinvention provides marked improvements in simplicity, economy andadaptability. Respecting the latter quality, as previously mentioned,various differing arrangements of the pick-up array may be made to adaptthe apparatus particularly to specific types of computational or otherselective switching functions such as automation controls. Figureillustrates an embodiment providing maximum versatility for ready set-upof new specific arrangements or quickly interchangeable set-upsofpreviously determined combinations without complicated or expensivechanges in tube structure.

In Figure 5, the numeral 52 designates a forward extension of the baseor supporting structure for the tube 10. An insulating plate 53, rigidlyfastened to the support 52 and facing the screen end 13 of the tube,carries a plurality of small jacks 54. The pick-up electrodes 23, 24,etc., disposed on the face 13 of the tube, are individually connected tocorresponding individual jacks 54 by short conductors 55, the latterpreferably being sufliciently flexible to avoid any strain on theelectrodes. Additional jacks in the panel 53 are also provided toaccommodate the primary amplifier output conductors 31a and 32b asshown.

The jacks 54 are adapted to receive the prongs or plugs 56 of a hollowgang connector 57 within which the plugs may be pre-wired in suitablecombinations as indicated in dotted lines. Obviously this internalpre-wiring may be made to establish any desired arrangement of thepick-up connections, in addition to that shown in Figure 2 An example isthe combination shown in Figure 6, wherein a and b electrodes alternateboth in the vertical and horizontal rows. As a further example ofadaptability, by initial provision of additional jacks 54 and plugs 56,a single tube may be set up for a number of different problems at thesame time. To illustrate, by use of a properly pre-wired combinationalconnector 57 the pickup electrode array may be divided into two or moresets of cooperative a and b electrodes, each set feeding to its ownprimary and differential amplifying system of the type described herein.To change from one type of set-up to another it is only necessary tosubstitute an appropriately pre-wired panel 57.

It will be evident that the above advantages of practically unlimitedversatility in set-up combination stem largely from the exteriorlocation of the pick-up system, which avoids the interior structuralcomplications and multiple lead-out difliculties obviously attendant onany system of multiple interior pick-up electrodes. With the preferredembodiment of the invention as illustrated herein the tube 10 may be ofany suitable standard type, as previously mentioned. While if desiredthe pick-up electrodes 23, 24, etc., may be attached individually to thetube face 13, Figure 5 illustrates a method of multiple attachment bywhich interchangeability or replacement of tubes is further facilitated.For this purpose the pickup electrode assembly may be attached directlyto a thin and flexible insulating sheet 58 which in turn is detachablysecured on the tube face 13 by any suitable means such as a border 59 ofadhesive cellophane tape or the like. By this provision replacement ofdefective or deteriorated tubes may readily be made without disturbingthe electrical connections or relative electrode arrangement of theoutput system.

The preceding description has explained Operational and structuralfeatures which render the present invention an improved generalizedswitching system of maximum precision, simplicity and adaptability. Forpurposes of the explanation the interrogation bombardment has beendescribed as of the moving or dash type, but obviously other types suchas the focus-defocus method may be used. Similarly, while the inventionhas been described throughout in preferred typical form, it is notlimited to the precise structures and procedures illustrated, as variousmodifications may be made without departing from the scope of theappended claim.

I claim:

In an electro-static look-up system for deriving solutions of ageneralized problem in a large number of variables, in combination, acathode ray tube having an interior target surface, an array ofspatially separated pick-up electrodes disposed on the external surfaceof said tube in capacitative relationship with said interior targetsurface, said tube having deflector electrodes adapted to direct thebeam of said tube to pre-determined spots of said target underlying saidpick-up electrodes in selective response to entered deflector voltagesrepresentative of pre-determined combinations of said variables, meansto connect said electrodes in two electrically separated groups eachhaving a common signal conductor, said pick-up electrodes of said twogroups being arranged in a pattern adapted to establish responses tosaid beam representing solutional elements of said problem incorrespondence with said entered combinations,

differential amplifying means having two input receiving means andadapted to establish a common output signal proportional to thepotential difierence between two input signals fed simultaneouslythereto, said output signal being of alternatively positive or negativepolarity dependent on the relative preponderance in amplitude betweensaid simultaneous input signals, and means to connect said two commongroup conductors respectively to said two input receiving means.

References Cited in the file of this patent UNITED STATES PATENTSHadekel Oct. 31, 1944 Luhn Mar. 11, 1947 Hartig May 11, 1948 Lesti Feb.28, 1950 Tuller Mar. 18, 1952 Bridges Ian. 15, 1957

